I was in same shoes as yours around two years ago. I feel your pain. I asked similar question on HN then (1). My advice is apply at startups that explicitly invite international candidates, especially the ones that lists 'can sponsor visa' info in their job postings. Even if they are willing to offer a job, it's just very difficult to get a visa to US. I have interviewed with one or two from Valley, it always came down to visa.
If you don't find a great startup, try looking for one in India. Hard to filter through awful lot of crappy ones, but put some time. Talk to as many startups as possible, don't just interview, but go to the offices, see how they work and try to work for a week before you join. You will find something good. Be patient, I must have talked to at least 40 startups face to face, went to at least 10 offices. It's funny though, at last I found my job through monthly HN-hiring thread.